The present invention relates to an electronic signal conversion system which includes an electrical signal to be converted and provides a unique and particularly useful way of converting the value of the signal, which is represented by the magnitude of the signal to be converted, said signal being alternating current (hereinafter AC), to a corresponding value of that signal, which is represented by the magnitude of the converted signal, said signal being direct current (hereinafter DC).
Heretofore, several systems for handling this type of electrical conversion have been taught by the prior art. Probably the best known systems of this type take a fixed amplitude AC signal and convert it to a fixed amplitude DC signal. This type of prior art system has the substantial drawback that it produces a fixed amplitude DC signal as a result of the conversion and requires a fixed amplitude input signal.
Typical examples of other AC-TO-DC Converter devices and methods are shown in U.S. Pat. No. 3,535,556, issued Oct. 20, 1970 to S. R. Hall, U.S. Pat. No. 3,491,252, issued Jan. 20, 1970 to H. Petrohilos, U.S. Pat. No. 3,721,891, issued Mar. 20, 1973 to A. J. Moses, U.S. Pat. No. 3,652,945, issued Mar. 28, 1972 to H. Nakane et al., U.S. Pat. No. 3,564,389, issued Feb. 16, 1971 to P. L. Richmond U.S. Pat. No. 3,488,598, issued Jan. 6, 1970 to E. Hoo, and U.S. Pat. No. 3,373,334, issued Mar. 12, 1968 to E. W, Geisz, et al.
The Hall, Petrohilos, and Moses AC-TO-DC Conversion devices convert variable frequency periodic inputs to their RMS or absolute value through the use of reference signals and other circuit means. The Hall AC-TO-DC Converter produces a pulse train rather than a DC output. The Petrohilos device produces a DC output proportional to the average value of the input. The Moses device produces a DC output proportional to the amplitude of an AC Input for a frequency of AC Input introduced into the device without the use of feedback. The drawback with any of these devices is that they have no isolation, are inaccurate, have no offset adjustment, and are not specifically directed at a single frequency input. Additionally, they do not produce a current output and require a reference signal.
The Nakane and Richmond devices convert broad frequency AC inputs to a DC RMS value without the use of a reference signal. However, neither of these devices is capable or discloses a method of producing current output; they both lack DC isolation; they both lack offset adjustment; and they are useful only in broad frequency inputs and do not deal with a single AC frequency input.
The Hoo and Geisz devices convert fixed frequency AC signals to DC signals. These systems take a fixed amplitude AC signal and convert it to a fixed amplitude DC signal for either power regulation or frequency control. This type of prior art system has a substantial drawback in that it produces a fixed amplitude DC signal as a result of the conversion and requires a fixed amplitude input signal, as well as a lack of accuracy and offset adjustment.
In the present invention, the input signal for any pre-determined range and frequency is introduced into the AC-TO-DC Converter wherein the signal is isolated, and normal and common mode noise eliminated. The AC-TO-DC Converter then rectifies, scales, filters, shapes, and amplifies the input signal to the form necessary or desirable for the output signal. There is no mechanical coupling and all input and output signals are allowed to be variable within predefined ranges. The present invention is completely electronic through the use of novel circuit techniques.